1. Field of the Invention
The present invention relates to an apparatus for trimming a layer of cut tobacco formed on a tobacco band of a cigarette manufacturing machine, and more particularly, to a trimming apparatus for intermittently increasing the thickness of the cut tobacco layer in the traveling direction of the tobacco band.
2. Description of the Related Art
In a cigarette manufacturing machine, a layer of cut tobacco is first formed on a tobacco band running in one direction. Then, the cut tobacco layer on the tobacco band is adjusted to a predetermined thickness by means of a trimming apparatus, and is fed from the tobacco band onto a paper web traveling in the one direction. As the paper web travels in this manner, the tobacco layer thereon is wrapped in the web, thereby forming a continuous cigarette rod. As the cigarette rod passes through a cutting section of the cigarette manufacturing machine at a predetermined traveling speed, it is cut into individual cigarettes with a given length.
In order to prevent the cut tobacco from falling off from the cut ends of each cigarette, the tobacco filling density of those portions of the cigarette rod in which the rod is to be cut is made higher than that of the other portions.
To attain this, the trimming apparatus has a function to increase intermittently the filling density of the cut tobacco in the cigarette rod to be formed, along the axis of the rod. An example of the trimming apparatus of this type is described in Japanese Patent Publication (KOKOKU) No. 51-17200.
This disclosed trimming apparatus comprises a pair of trimming disks. The disks are arranged right under the tobacco band with their respective peripheral surfaces in rolling contact with each other so that they are rotated in opposite directions. As the cut tobacco layer, along with the tobacco band, passes the pair of trimming disks, therefore, a surplus of the tobacco layer is scraped off by the rotating disks, whereby the thickness of the tobacco layer is made uniform.
However, each trimming disk has a plurality of pockets on its peripheral edge, and each pocket of one disk and its corresponding pocket of the other disk cyclically meet each other right under the tobacco band as the disks rotate. Thus, the thickness of the cut tobacco layer on the tobacco band is not uniform with respect to the traveling direction, and is increased by a margin equivalent to the depth of each pocket every time the corresponding pockets of the pair of trimming disks meet just under the tobacco band. In consequence, the cut tobacco layer fed from the tobacco band onto the paper web has first regions of high tobacco density and second regions of low tobacco density which are arranged alternately in the traveling direction of the web.
When the cut tobacco layer on the paper web is wrapped in the web to form a continuous cigarette rod, thereafter, the filling density of the cut tobacco in those portions of the rod which correspond to the first regions is naturally higher than that of those portions which correspond to the second regions. If the cigarette rod is cut in the respective centers of specific portions corresponding to the first regions, therefore, the cut tobacco can be prevented from falling off from the cut ends of individual cigarettes, since the filling density of the tobacco is higher in the vicinity of the cut ends.
As is evident from the above description, each specific portion in which the cigarette rod is to be cut must be formed for each interval which is as long as each cigarette, and the cigarette rod must be cut accurately in the center of each specific portion. Therefore, the cigarette rod must be cut in synchronism with the phase of advance of the specific portions thereof, that is, the rotational phase of the pockets of the trimming disks.
If the operation of the cigarette manufacturing machine goes wrong, or if troubleshooting is carried out, the cutting timing for the cigarette rod and the rotational phase of the pockets of the trimming disks may fail to be synchronous due to some cause.
In this case, the rotational phase of the pockets of the trimming disks should be adjusted in order to re-establish the synchronism between the cutting timing and the rotational phase. This adjustment must, however, be made after stopping the operation of the cigarette manufacturing machine. To check the adjustment for accuracy, moreover, the manufacturing machine requires a trial run. Accordingly, adjusting the rotational phase of the pockets of the trimming disks to the cutting timing for the cigarette rod takes a lot of time, thus considerably lowering the operating efficiency of the cigarette manufacturing machine.